In most of the present-day cement mills and coal mills, the roller bowl is driven via a gearing by a motor disposed laterally adjacent the gearing. In the case of such mills having a horizontally disposed roller bowl, the rotary motion of the motor is transmitted via a coupling to a bevel gear step, through which the rotary motion being initially about a horizontal axis is redirected to a vertical axis. In most cases a planetary gearing is used as the gearing, which moves the roller bowl via an output flange; alternatively or additionally, use is often made of a spur gearing, too.
For example, FIG. 1 of Swiss Patent No. 658 801 discloses a structure of this kind.
Manufacturing bevel gear steps is very expensive, in particular if they are to have great precision. Moreover, bevel gear steps generate very large radial and axial forces in the bearings which are to be absorbed, resulting in correspondingly extensive dimensioning.
U.S. Pat. No. 4,887,489 proposes to place the motor with vertical axis laterally adjacent the gearing and to transmit the rotary motion by means of a cascade of gears into the gearing, since in this way no bevel gearing is required.
FIGS. 2 to 4 of Swiss Patent No. 658 801 propose to dispose an electric motor with vertical axis below the gearing in the case of a roller bowl mill. In FIGS. 3 and 4 of Swiss Patent No. 658 801 the roller bowl mill is held by means of a mount or pillars, wherein the mount and the pillars, respectively, are supported on a foundation. In these cases, the electric motor was sunk into the foundation, so that constructional height can be saved above the foundation. In FIG. 2 of Swiss Patent No. 658 801 the roller bowl mill is held by means of pillars supported on a foundation. In this case the electric motor is disposed between the pillars and separately supported on the foundation between the pillars.